Intel CPUs impacted by new PortSmash side-channel vulnerability

Re:Intel CPUs impacted by new PortSmash side-channel vulnera... by gravypod on Friday November 02, 2018 @05:21PM (#18366885)

Unfortunately this contention is the exact reason this isn't done. Similar workloads (from the same program) will perform poorly in the same SMT groups. You can try this in windows using the core affinity of processes. You'll find that when one application shares both HTs it will perform much worse.

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Re:Intel CPUs impacted by new PortSmash side-channel vulnera... by zrav on Monday November 05, 2018 @06:02AM (#18381371)

Under optimal conditions (rendering) enabling SMT on Intel gives just ~30% extra performance, ~40% on AMD (usually much less), so of course you can't compare the additional thread provided by SMT to a thread running on another, otherwise idle core.

Scheduling only threads of the same process on a SMT group at a time is the easiest portsmash mitigation while still retaining some of the SMT peformance benefit.

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